Add tests, add docu, use subpackage.

src/main/java/io/kokuwa/micronaut/logging/LogbackUtil.java

@@ -0,0 +1,50 @@
+package io.kokuwa.micronaut.logging;
+
+import java.util.Objects;
+import java.util.Optional;
+import java.util.function.Supplier;
+
+import javax.inject.Singleton;
+
+import org.slf4j.LoggerFactory;
+
+import ch.qos.logback.classic.LoggerContext;
+import ch.qos.logback.classic.turbo.TurboFilter;
+import io.micronaut.context.annotation.BootstrapContextCompatible;
+import io.micronaut.context.annotation.Requires;
+import io.micronaut.core.annotation.Internal;
+
+/**
+ * Utility class for Logback operations.
+ *
+ * @author Stephan Schnabel
+ */
+@Requires(classes = LoggerContext.class)
+@BootstrapContextCompatible
+@Singleton
+@Internal
+public class LogbackUtil {
+
+	private final LoggerContext context;
+
+	public LogbackUtil() {
+		this.context = (LoggerContext) LoggerFactory.getILoggerFactory();
+	}
+
+	public <T extends TurboFilter> Optional<T> getTurboFilter(Class<T> type, String name) {
+		return context.getTurboFilterList().stream()
+				.filter(filter -> Objects.equals(name, filter.getName()))
+				.filter(type::isInstance)
+				.map(type::cast).findAny();
+	}
+
+	public <T extends TurboFilter> T getTurboFilter(Class<T> type, String name, Supplier<T> defaultFilter) {
+		return getTurboFilter(type, name).orElseGet(() -> {
+			var filter = defaultFilter.get();
+			filter.setName(name);
+			filter.setContext(context);
+			context.addTurboFilter(filter);
+			return filter;
+		});
+	}
+}